The invention relates to a circuit arrangement for checking liquid food for contaminants.
The checking of liquid food, for example of milk, beer, fruit juices or the like, during the processing and filling thereof has hitherto been effected by taking random samples. This does not reliably exclude any possibility of a contamination caused by acid, lye or water not being discovered and liquid food that is unfit for consumption reaching the consumer. Of particular urgency is the continuous automatic checking of multi-circuit filling plants, more especially milk filling plants in dairies. Plants of this kind are frequently operated in such a way that milk is filled in in one circuit, whilst the other circuit is cleansed by means of acids, lyes or the like. For greater flexibility the two circuits are interconnected, the connection being normally blocked by a solenoid valve. If this valve is not fully shut or is opened by mistake, then lye or acid can pass from the circuit which is in the process of being cleaned into the other circuit and thus into the milk.
Automatic checking of liquid food for contaminants by means of conductivity measurements has so far not been carried out since the nominal conductivity value can fluctuate considerably from batch to batch. For example, the basic conductivity of milk is subjected to seasonal fluctuations and the different grades of milk (homogenised milk, skimmed milk, buttermilk, etc.) have different basic conductivities. Consequently, it would be necessary to input for each new batch which is introduced into the monitored system not only the nominal value but also the upper and lower limits of the allowable deviations. However, such settings can only be effected by experts, who are not always available at any time in the processing establishments of liquid food.